Fat plants

What has my cactus


Question: What has my cactus


Hi, I recently came into possession of a cactus, the classic round and fat, about 30 cm in diameter. At the top, however, it has a white frothy part, sometimes even hard. What is it? Will the cactus die?
Thanks,
NS

Answer: What has my cactus


Dear Neviana,
the world of cacti is very wide, they are succulent plants that live in a large area ranging from the southern states of North America, to Central America and down to the arid and semi-arid areas in South America; in total we are talking about a few thousand species of plants, which, although non-experts may at first sight appear to be all the same, have rather different forms, development and needs. Speaking of a spongy white area, I cannot understand what it could be: consider that a genus of cactus, the Melocactus, produce a sort of small hat on the apex, composed of thorns similar to thick hairs, white, red or orange; try looking at photos of melocactus online, because if your plant belongs to this species, its white hat is completely normal, but the plant is not easy to grow, and therefore will need your care to survive. If, on the other hand, the clear part is not made up of thorns, but from the epidermis of the cactus itself, which is bleached, it could be a particular fungal disease, which should be treated with a foliar absorption fungicide, to be sprayed on the plant, which will absorb it from the stem and will have it in circulation for a few days, in order to kill all the possible mushrooms present. Consider that in this case the presence of a fungus is often caused by excess water in the soil, and therefore learns to water your cactus only when the soil is dry; something that in winter can mean no watering, but in July it can result in watering every other day.
Spots and signs of any kind on the apex of a cactus can also indicate a sort of scarring due to various types of damage, such as bumps, hail, and insects that have been eradicated. Much depends on the shape of the clear area, on its consistency, where it is on the cactus: signs of hail will be distributed over the entire surface, while the impact due to an object that has fallen on the cactus, could be anywhere. Everything depends on how your plant is: if it is well, it has a stem of a beautiful color, turgid, that does not have soft areas, then it could actually be a previous collision, which has left a mark, and nothing more. If, on the other hand, in addition to the clear zone, the plant also shows other symptoms, it is more likely that it is a fungal disease, which must be treated quickly, if you do not want to see the whole plant fall prey to the rot. If the cactus was perfect when you bought it, and suddenly it is developing this particular spot, then it is more likely to be a fungal problem: cure with a fungicide, and possibly, if the area is large, first detach it from the plant with a sharp knife, and dust from cupric fungicide.